Growth, development and maintenance of integrity of the fetal brain require a continual supply of oxygen and potential energy, predominantly glucose. High energy compounds formed during the oxidation of glucose are necessary to perform the internal work required for normal enlargement and differentiation of the fetal brain. Most of the chemical energy metabolized by brain during gestation ultimately becomes heat energy which is lost to cerebral venous blood. The objective of the research proposed in this grant application is the establishment of standards of normality of cerebral energy metabolism of the fetal lamb using two techniques: 1) measurement of glucose consumption in discrete areas of brain by the (14C) deoyglucose technique; 2) measurement of regional brain heat production by observations of temperature change following complete but reversible cerebral ischemia. Further studies will evaluate local cerebral glucose consumption and heat production in conditions of possible fetal distress including fetal hypoglycemia.